1. Field of the Invention
This invention relates generally to the controlled cooling of the molten flat glass ribbon as it passes through the tin float bath at a continuous rate. Manufacturing flat glass comprises the delivering of molten glass to a bath of molten tin and advancing the glass along the surface of the tin bath under thermal conditions that do not contaminate the internal atmosphere. Such contamination is detrimental to both the glass product and the molten tin. Glass at approximately 1900 degrees F enters the bath from the melting tank and at approximately 1200 degrees F exits the bath to a cooling lehr. In present installations the temperatures in the bath are maintained with electrical resistance heaters suspended from the roof over the flat ribbon of glass. Such electrical heaters do not contaminate the bath atmosphere and have been used over the past twenty year period.
2. Description of the Related Art
Attempts to burn natural gas over the bath by the glass industry failed the industry's contamination requirements. This invention originates a unique application of the automatic recuperative natural gas burners to flat glass production for the first time. Combustion air and natural gas are ignited and burned within a heat-radiating chamber. The residue from burnt gases is exhausted externally to the bath and has no contact whatever with the atmosphere inside the bath. Recuperative burners have been used previously by the steel and aluminum industries, but never in the tin float bath process by the glass industry.